It is known to change rolls in a rotary web fed printing machine by adhering a replacement roll on a roll then being run on the printing machine, see for example German
Published Patent Application 22 24 733, Ketteler. The structure described in this reference provides for adhesion of the replacement web to the old or first or expiring web. Upon such adhesion, a short remainder length of web from the first or old roll will remain. The roll changer includes a frame, pivotable about a horizontal axis, which retains e.g. two rolls; one, the old or first roll and, further, one or more replacement rolls. The roll-off speed of the web then being handled in the printing machine is controlled, so that the tension of the web passing through the printing machine will be appropriate for printing on the paper web. Additionally, apparatus is provided to accelerate the replacement roll, and synchronize the speed of the replacement roll with the linear speed of the running-off web from the first or old roll. A brush applies the old web against an adhesive tip on the new roll. A knife is provided for severing the remainder of the old web when the old web and the replacement web have been adhered.
Control of the rolls is carried out electronically, by providing an electronic pulse source which provides a pulse train which can indicate the position where adhesive is to be applied on the replacement roll and, additionally, controls the brush to press the old web on the new web. The knife to cut off the remaining flap of the old web is also controlled by the electronic control system. The pulses of the pulse train are evaluated by digital counters, timing elements, or the like.
The system, as heretofore used, includes a replacement roll which first has an adhesive applied thereto, and which is fitted on the frame of the roll changer. To initiate a roll or web change, the adhesive is pre-applied as an adhesive tip on the replacement roll and the web from the first or old or expiring roll is then pressed by a brush against the replacement roll which, at that time, has been accelerated to the running speed required to roll the web off the replacement roll and feed it to a printing machine. The old roll, in effect, engages or grips the beginning of the new roll which is to be pulled off, and carries it along; the expiring web pulls off the replacement web from the replacement roll, thereby initiating rolling off of the replacement web from the replacement roll. The cutter apparatus severs the web of the old roll from the now effectively dual webs. This leaves a web portion or flap of the old or expiring roll, which is pulled by the printing machine into the printing stations.
It has been found that this loose flap can catch in the printing stations and may lead to damage in the printing machines; under extreme conditions it may lead to tearing of the web which includes tearing of the replacement web, which can deposit itself somewhere within the printing machine system, to interfere with printing and/or cause shut-down of the entire printing machine system to remove the misfeed of paper in the printing machine.